Subdivided service system of radio broadcast distribution



I 1 E. E. CLEMENT K sUBDIvI-DED SERVICE SYSTEM oF RADIO BROADCAST DISTRIBUTION Filed March 22, 1924 2 Studis-Sheet'a4 70 MM? 0c/u asc/Aurox l'My V'riveiition relates to systems of radio.k

Patented MQ; 1925.

v,UNITED STATES PATENT-critica. I

i I.` CLEMENT, .0F WASHINGTON, DISTIICT OF COLUIBIA "WARD F. OOLLADAY, OF WASHINGTON, DISTRICT 0I eunnrvrnnn sEEvIcE SYSTEM Application sied To all whom 'it may concern:

Be it known that I, EDWARD E. CLEMENT, .a 'citizen of the United States, residing at ashingt'on, in the District of have invented certain new and provements' in Subdivided Service useful Im- Systems of Radio Broadcast Distribution, of whichv the following is a specification, reference being had therein to the accompanying drawings.

broadcast distribution and has for its object the organization of a system ycapable ofgiving service to subscribers in regional groups, which may be related to each other by a general organization corresponding to the long distance telephone organization. f

I attain my object by relating my subscribers in each area to one or more local central oiices, byr means vof wired circuits, which may conveniently be telephone line circuits. Each subscriber is provided with a standardized form of receiving radiophone, and each central oflce is also provided with receiving radio-phones, but much more elaborate and powerful than those at the service, that ing, is received by the subscriber direct but when lie desires any station except those that are listed as. local, he "secures a long distance connection through his line wires to a central otlice radio receiving set capable of picking up and receiving the station lie..

wants. The subscribers instrument may conveniently be av single tube regenerative set with common batteryl connections, taking all its current supply over the subscribers wired circuit. The central office radio sets may conveniently be superheterodynes cr the equivalent thereof, capable of receiving from distant stations and transforming the carrier wave length so as to 4:relay or retransmit the original modulations over the subscribers line on a long Vcarrier wave, preferably at superaudio frequency, such as to 60 kc. per second.

The advantages 0f this arraiigementvwill be apparent on brief consideration. A single tube set, is usually sutlicient to give excellent results with local. broadcasting, yand by using a dynamic receiver, itis even possible 'to operate therewith a moderately loud table talker or loud speaker. For distance work, the antenna or equivalent wave Columbia,

subscribers stations. Local is to say, local broadcast-k ytickler loop or regenerative coil, 15y

strument to line COLUMBIA.

,me *ffm 1f- HEISSUED collector is unnecessary, and the input side Assrcivon rc m- 1sA connected through a timed coupler to the` line circuit. The same tube detector in the subscribers set then receives the distant signals on long waves, without the necessity of elaborate tuning on the part of the subscriber.

the accompanying drawings, in which4 Fig. 1 is a diagram of a subscribers station. Y i

Fig. 2 is alconnectedv dia ram of the central otlice end ofthe subscribers wiredline circuit, Y showingk terminal devices and switching means therefor.

p For the local service, since no op; erators are required, a at rate may Fig. 3 is a diagram showing a central cf- 1 fice superheterodyne receivery with its, terf minal-switching device and an operatoi'7s supervisory circuit. Y Referring to .the drawings, Figs. 1, 2, and 3 are all to be-read together, the dotted lines aa and bb in Figures land 2 being spaced apart to indicate distance between the sube scribers station and the central ollice; and

the dotted lines cc in Figs. 2 and 3 being identical and meant to be brought together,

so thatthe jack J2 in Fig. 8 P ink Fig. 2 will be adjacent Fig. l represents a subscribers instrument. 1 is a detector tube with the usual filament 2, rid 3 and plate 4. 5 and 6 are rheostats, gis a choke coil, 8 is a telephone transmitter of standard blridged across `the line t ie and the lug wires 9' and 10 by to each ot er.

type adapted to be push button or key '11, 'which however, t

opens as soon aspressure is removed from,y

it. 12 is the subscribers headphone, 13 is a loop antenna for local receiving, 14 isa usual tuning condenser across the loop,

18 and 19 are tuning condensers for the distance circuit, 20 and 21 are radio frequency ment for either ong distance or local re- H Y is the choke coils included in the branch of the ordinary telephone 'set 22, and 23 is a gang switch ada ted to connect the instrui ceiving to the telephone line wires 9--l0,

or to disconnect it entirely therefrom, at will. There are no batteries at the subscribers station, all energy for all purposes being supplied over the metallic circuit` 9-10, from the telephone exchange central office shown in Fig. 2.

Fig. 2 shows one telephone line 9-10 with the switching terminals in the form of springjacks JK-J, a line relay L, battery B, cut-off relay C, a signal lamp S. These elements of the line, as shown, are all old and well understood, and for the purpose of connecting this line with others for tele phonic use, standard IVestern Electric No. 1 switchboard cord circuits are supposed to be employed, which however, are not shown separately herein. The line 9-10, and any number of other lines assumed to be taking radio service, must be supplied with centralized current during operation ot' their radiophones without keeping their signal lamps S burning, this app ying to both local and long distance service. For local service no other connection is required at the, central olice, but for long distance, that is to say, for receiving from distant stations, the subscribers line must be connected with a central oiiice receiving instrument such as that shown in Fig. 3. The simplest form of connection is a direct connection from the line wires 9-10, to the bus bars 24--25 of the receiving instrument. This connection is shown in Figs. 2 and 3 as established by means of keys K-K which may be left normally closed, because radio frequency condensers are included in the circuits. In su'ch case the subscriber can secure long distance service by merely turning his own switch into the proper position. However, this permanent connection would give him access to only one central office receiver, and he would be limited to the program received from stations selected by the central oflice operators. In order to give him a wider choice, I have indicated also interchange able switching means consisting of plugs P--P cooperating with the line jacks J-.I on one hand, and with terminal jacks J2 J3 which typify terminals of any desired number of receiving instruments.

The amount of current consumed in the arrangement herein indicated at the subscribers station, using a UV 199 tube, is 45 milliamperes.

Referring to Fig. 3, the superheterodyne receiver therein shown of itself and as to the details of its construction, forms no part of the present invention. It may be replaced by any convenient Jform of receiver which will give equivalent range, selectivity, and volume of output. As shown it com prises as its essential elements the following: antenna circuit 26, coupler 27, input circuit 28, provided with the usual tuning devices including condenser 29, and a load coil 30 which may be cut in or out by means of a shunting switch 31, first detector tube 32, coupler 33, and three stages of radio frequency amplilcation 34, 35, and 36, each includin a triode tube and transformer; also a loca oscillator circuit 37 including the tube 38, and the usual coils to connect it with the input circuit 28. This oscillator circuit 37 is tunable by means of the condenser 39 and the long wave switch 40 to any Wave length through the usual range of broadcasting, as for example from 200 to 600 meters inclusive. To this circuit l have added a local modulating circuit 41, having a microphone transmitter 42, and a modulator tube 43 with the usual connections. It is to be understood that this arrangement is typical only, and may be varied without departing from the invention. T he batteries A and B for this receiving set are indicated in the upper part of the ligure,

and the power connections mav be varied, or additional batteries employed, as required in practice. The choke coil which isusually included in the battery branch of the standard modulator circuit is also shown for convenience at 44 in the upper part of the figure.

In order that a continuous program may be furnished when subscribers are connected to long distance, giving them for example a part of the program from a distant station, and then without changing the tuning or their connections, giving them other parts originated locally I add a second local oscillator circuit 45, having a coil 46 so related to the coupler 27 that local oscillations in the circuit 46 may take the place of the carrier waves received from a distant station, thus maintaining the heterodyne effect and the` flow of long waves amplified at 34, 35 and 36 to the subscribers line wires 9-10 and so to his station receiver. Local .modulations may then be imposed upon the long waves thus transmitted, by means of either the modulator 41, or a suitable modulator connected to the balancing local oscillator circuit 45.

For the purpose of tuning and supervision, I have shown an operators receiving set 47, comprising the usual elements ot'the tube 48, tuned input circuit 49, and a key 5() by which the set may he connected Ato the output circuit 51 of the superheterodyne. The same operators set 47 may be used with a plurality of main receiving sets. asindicated by the multiple key 50". Also. the output circuit 51 of each long distance receiving set may have bus bars 24-25 connected to a plurality of switching terminals shown as multiple jacks J2 .T-1 and switching key K', so that a plurality of subscribers lines may be interchangeably connected thereto. It is to be observed that if thev'olulne of output in the circuit 5l is in-y sufficient for a number of lines to be served, ,any vdesired andy ,suitable arrangement of tubes 'ory equivalent devices may be employed, to increase the same, either between the c-ir` cuit 5l and the bus 24-25for between the bus and the switching ,terminals and subscribers lines. Such modifications are well within thescopeof the invention, and would include the insertion when necessary of repeaters and amplifiers in the circuits 52-43 leading tol individualsubscribers lines.

y It should particularly y*be observed inthe present case that I have shown no second detector in Fig.l 3thevoutput'circuit 5l delivering a carrier wave atlow or beat radio frequency.v That isto say, transmission of the received and amplified waves from the receiving setshown in Figi?) over the subscribers lines is at superaudio frequency,

. whichjis preferably maintainedy constant, re-

gardless of the lwave length of the station lbeing received at any given time on the antenna circuit 26'-27. The second detector is the tube ly at the subscribers station, and this arrangement :enables me, by providing the proper means, andby properly tuning theradio branches of the lines, to maintain `continuous radio service without interfering with the use of the subscribers wires 9-10 for vsimultaneous telephonie service. Conversely, `the telephonie currents or audio frequency waves, ywillvnot disturb the radio receiving, although this is not so important, because inany combined system of this'type, preference must be given telephone service. At the subscribers station,`the"choke coil 7 guards the iilament'circuit from both radio and telephone audiocurrents while the high resistance, in the plate circuit'54"(of the order of 20,000 ohms) is sufiicient to prevent shunting of the' telephone apparatus at the station 22. w` t "Referring"k to Fig. 2, the plug circuit I3-P is typicalfof a` long distance radio connecting circuit, by which the subscribers line 9-10 through a vjack .I or J and a trunk `jackJzor J3 in Fig.` 8, maybe connectedto receive anydesired'distant station. Thiscord circuit is what is known as the lStandard Western Electric No; l switchboard cord circuit,with listening and ringing keys KLAKs respectively, repeating coil RR, supervisory elements s--s,` supervisory relays Tfr," and the usual balancing and byJ Vpass v"resistances 1 The main` battery Bv is supposed to 'have its busses connected in bridge with thesecord circuits, and in the p Vdiagram its positive pole is shown grounded as usual'. For specialy radio service, however, this ground may be omitted, a separate battery B being then employed. Since all of the'batterie's shown lherein arek at the vcentral station, they may be combined into one.v or may be umade separate unit-s, as circumlike.

stancesand vgood practice :may dictate. In

exchanges carrying a heavy radio load,fit may be advisable to providea separate vpower plant, which may conveniently be used in parallel relation tcthe telephone power plant, but the relation of the two load "curves, that'is the radio load andthe telef phone load, is such that only' in very exceptional cases will their peaks coincide oneven approach Veach other. The main telephone peaks occur approximately between 1()` and 11 in the morning, and 2 and 3 in the afternoon, with subsidiary peaksat one or two points between 4 and 7 p. m. The radio programsusually come on between 3 and 4 in the afternoon and after'7 in theevening. Subsidiary program peaks would be between 2 and 3 in the kafternoon'a'nd 6 and'7 in the evening, with occasional concentration at other hours, vas'for example when a special speech is broadcasted from Congress, or the The variations in the telephone load are due to well established business andy social conventions but'y the distributionof the radioy load, (or programs) is to a great eX- tent under the 'control of those who do the broadcasting. The diurnal variationsn efiiciency of wave` transmission through; the' fether render distance l.receiving more eiiective at night, and this coincidesy with* the hours of leisure of the majority of subscribers, as well as with the low or fiat portion of the telephone load curve. In general "therefore, it may be said that the two servcontrol the continuity of the ordinary kcord circuit connections `61, 62 and 64: to the plug P', from the battery B and repeating coil R. The conductors 64--65 and 66 leading to the plug P are left intact at all times inv Vorder to furnish operating current to the subscriber, andv to supervise the connection by means ofthe la1nps1s,with the anclllary purpose of operating the'cut-oii relay Gand putting a special' rtone test on the multiple jacks, so 'that the line will not test busy to telephone operators.' This tone test' 68 controlled by a switch 67 closed wheny the cord is inusefor radieuse, and opened along with the contacts .54-55 when in use 'for telephone service. When'the contactsv 54, 55`and` 67 are closed for radio service the contacts 56,- 57 and 58 are opened, althoughv it has been found that this is not absolutely essential to good radio transmission. One winding of each coil R is lett between the battery B and the conductors (i-L and GG, and may be supplemented by a radio choke coil, if the battery l is the same as or is connected with the main telephone battery, the purpose beingto keep the radio waves oil the battery busses.

As previously pointed out, instead of being connected through the cord circuit 13h-P',I the subscribers line connected to the central oiice distant receiver of Fig. 3 by means of the circuit 52-53, provided with switches at both ends. As a matter of fact, the circuit 52-53, instead otv being individual` may be common to a number of lines as indicated by the branchvwires 52 and 53, the single pair 52-53 thus becoming an extension of the output bus. The transmission over the line 9--10 is facilitated by tuning both ends of the line, as well understood in the art, and I therefore include a coupler l69-70 and a tuning condenser 7l, the elements 70--71 being bridged across the line by the key K. .These .elements in conjunction with the cor- -responding elements 17-19 at the subscribers station not only render the transmission better, but eiectually absorb the radio Waves and block audio waves over the line. The elements 69-60-71 ind their counterparts in the cord circuits at 59-60 and 7 3, for the same purpose; and since there is thus a couler always interposed between the output us of the superheterodyne and the subscribers line, the last transformer 74 shown connected with the output circuit 5l may be omitted if desired. In the cord circuit 4I have also shown a tunin condenser 72; and it is to be noted that in tie output circuit 5l (Fi 3).there are two fixed condensers, inten ed to prevent any possible short-circuiting of telephone or battery currents through the secondary of the transformer 7 4. These may be omitted if tuning condensers are emplo ed as at 72 in series with the coil 59.

'lyhe operation of my system thus described is as follows:

The subscribers station in Fi 1 is shown with all parts in a condition o disuse. If the subscriber desires telephone service, he. removes his telephone receiver from the hook and thereby signals central through the parts L and S, as'usual. A cord circuit which may be that shown at P-P, with the contacts 56, 57 and 58 closed and the contacts 54:--55 opened, is then employed, to answer, test, connect, ring the wanted subscriber, and supervise, as usual. If, on the other hand the subscriber desires radiophone service, he sets his switch for local or long distance, as the case may be. Assuming that he desires only local receiving, and that sufcient battery current for the filament 2 9-10 may bel may flow through the line without disturbing the central ofiice signal S or protective devices, he need do nothing further. If he desires long distance receiving however, he calls the operator in the usual way, either by means of his ordinary telephone set, or by means of theV transmitter 8 controlled by the push button 1l associated with the radio set. In accordance with standard practice, distant stations will be numbered, and in response to the inquiry Number, please, the subscriber gives the number, as for example Radio, 412. The operator then connects him with the superheterodyne receiver of Fig. 3 which can give himA the station he wants, and if necessary communicatesV at the same time through an order circuit with the radio operator in charge of the radio receiving apparatus.` As an alternative, and in accordance with long distance telephone practice, the localor A operator may answer the call and learning it is for radio may .communicate with the radio operator over an order circuit, and the radio opera-tor will then connect with one of the multiple terminals of the callingA subscribers line, ascertaining direct from the subscriber what station he wants, and setting up the necessary radio connections accordingly.4 This arrangement has the obvious advantage of avoidlng a tie up of the operators cords on an A board or answering positions. This method may be practiced with the same circuits and apparatus shown in Fig. 2, if it be understood that the cord circuit P-P is a radio operators cord circuit, and that while the A or answering operators on a telephone switchboard ma have similarly equip ed cords for convenience, the load is carriedp on the radio switchboard, containing multiples of the subscribers line, and this radio switchboard may be automatic or manual or semi-automatic in its mode of o eration. Thismethod has also the additiona advantage that the calling and switching to the ra ioboard -may be simplified by establishing a conventional form of radio callin which may be made by flashing line lamp The A operator perceiving a line lam to Hash, would know that the line desired lbng distance radio connection, and would pass the call to the radio operator as before stated, using an order circuit. If the lamp burns steadily, it would indicate a desire for telephone connection, and where the subscriber is using his instrument for local radio receiving there would preferably be no indication at all on the lamp S.

I claim: Y

1. In a radiophone system of broadcast distribution, a central station and subscribers stations, radiophone receiving sets at the subscribers stations each comprising a .thermotic tube with plate and filament circuits therefor connected to the line circuit for current supply, a common source of current at the central station connected to the line and of a suiiicient voltage to operate said plate circuits thereover, voltage reducing means connected between the line and the filament circuit, an antenna at the subscriber`s station, means for operatively connecting the input circuit of the subscribers set with either the antenna or the line, and means operable upon the switching of said input circuit from the antenna to the line to automatically change the tuning of said receiving set from short Wave lengths to long vvave lengths.

2. In a radiophone system of broadcast distribution, a central station and subscribers stations, radiophone Areceiving sets at the subscribers stations each comprising a thermotic tube with plate and filament cir cuits therefor connected to the line circuit for current supply, a common source of current at the central station connected tothe lne and of a sufficient voltage At0 operate -aid plate circuit thereover, voltage reducing means connected between the line and the iilament circuit, a receiving antenna at each subscribers station, meansV for distributing broadcast mattei' over the lines by wired rado, and means at a subscribers station for switching the subscribers radio receiving apparatus from radio to Wired radio. 3. Ina radiophone system of broadcast distribution, a common battery telephone `system having subscribers stations and lines interconnecting the same, radiophone receivers at the subscribers stations supplied with operating current from the central station over the lines, means at the subscribers stalion for receiving radio broadcast on the radio receiver, means for distributing broadcast matter over the telephone lines by wired radio, and means at the subscribers station for switchingthe subscribers radio receiver from radio to Wired radio'.

4. In a radiophone system of broadcast tral station forv supplying current over the lines, lradio transmitting means at the. central station, Vlink circuits at the central station for connecting said radio transmitting means With the subscribers lines for transmission thereover by Wired radio, means for signalling the central station from the subf scribers station Vover the line, and means -at the subscribers station for switching the connection of subscribers lines with each other or to the connection of said transmit# ting means With subscribers lines, and

switching means at the subscribers station for switching the radio receiving set from radio reception to line radio reception.

G. In a radiophone system of broadcast distribution, a central station and lines leading therefrom to subscribers stations, radiophone receivers at the subscribers stations arranged to be supplied with operating current over the line, means 'atthe central station for supplying current. over the lines, radio transmitting means at the central station, link` circuits at lthe central station, switching means associated with a link circuit for adapting teither to the interconnection of, subscribers lines with each other or to the connection of said transmitting means for switching the radio receiv? ing set from radio reception to line radio reception, together with means for central station supervision of the operation of a `subscribers radiophone set at all times.

7. In a. radiophone system of broadcast distribution, a central station and subscribers stations with lines interconnecting the same,radio receiving sets at the subscribers stations .connected With the line to take operatingcurrent therefrom a radio vreceiving antenna for each subscribers receiving set, means at thecentral station for supply ing current over the line, for operating'the subscribers7 radiophone receiving sets, means for transmitting a low frequencycarrier current over the lines, a low frequency receiving circuit at each subscribers station tuned to the said low frequency carrier current, and means at each subscribers station for connecting the input sidel of the said radio receiving set to either thefantenna circuit or through the low frequency tuned re-y ceiving circuit to theline.

In testimony whereof I hereunto affix my signature.

EDWARD E. CLEMENT.

llO 

